Thermal processing torches, such as plasma arc cutting torches, are widely used in the cutting, gouging and marking of materials. A plasma arc torch generally includes an electrode, a nozzle having a central exit orifice mounted within a torch body, electrical connections, passages for cooling, and passages for arc control fluids (e.g., plasma gas). Optionally, a swirl ring is employed to control fluid flow patterns in the plasma chamber formed between the electrode and the nozzle. In some torches, a retaining cap can be used to maintain the nozzle and/or swirl ring in the plasma arc torch. In operation, the torch produces a plasma arc, which is a constricted jet of mostly ionized gas with high temperature and that can have sufficient momentum to assist with removal of molten metal.
Traditionally, a plasma arc torch can cut metal workpieces (e.g., stainless steel or aluminum workpieces) using a plasma gas, such as nitrogen N2, a mixture of 35% hydrogen and 65% argon (H35), or a mixture of 95% nitrogen and 5% hydrogen (F5). Because these gases are relatively expensive to produce and obtain, they can increase the overall cost of torch operations. In addition, cut speeds are limited by cut quality considerations.